This invention relates to a grinding arbor. In its more specific aspect, this invention relates to a grinding arbor for thread cutting tools such as chasers and the like, and especially an arbor for holding a chaser when grinding the chamfer.
Threading tools such as cutters or chasers and the like for cutting and finishing screw threads typically have a cutting face comprising a plurality of teeth and a beveled portion known as the chamfer which leads the tool onto the work. A precision ground chamfer is essential for cutting accurate threads. Because of wear, chasers must be resharpened frequently at the chamfer, usually a few thousands of an inch at any one resharpening. Further, chasers are employed in a set, e.g., four chasers to a set, and unequal grinding of the chasers in a set will cause the chasers to cut unevenly.
Chasers therefore cannot be ground by hand. It is conventional for this purpose to use a grinding fixture designed and operated so that all chasers of a set can be resharpened at one set-up. In this manner, the chasers are uniformly ground. However, these fixtures require numerous settings and exceedingly fine adjustments by a skillful mechanic. The chaser is inserted into a holder which is then clamped to the fixture and set to the proper chamfer clearance angle. The fixture is fed forward by hand to bring the chaser in contact with the grinding wheel wheel until it contacts a stop. The procedure is repeated for each chaser of a set at the same setting to insure uniformity of chamfer.
Chaser grinding fixtures have numerous disadvantages. The fixture is relatively expensive. More importantly, extreme precision in setting-up the operation is essential, which inherently takes considerable time, and only one chaser at a time can be ground. Notwithstanding the extreme care given, it is still difficult to achieve uniformity of chamfer among the members of a set.
It is the purpose of this invention to provide a grinding arbor which overcomes the disadvantages of the prior art grinding fixtures, and particularly to provide an arbor whereby all members of a set may be ground uniformly.